SteamOS will be made available when the prototype hardware ships. It will be downloadable by individual users and commercial OEMs. (But unless you're an intrepid Linux hacker already, we're going to recommend that you wait until later in 2014 to try it out.) We'll post info soon about that. Oh, and stay tuned for the in-home streaming beta to begin soon, too!

So my big question is, what refinements has Nvidia made to SteamOS? Nvidia was working with Valve on this project. Will SteamOS run games better than say Fedora+Steam+Nvidia_blob? Can't wait to get my hands on a steam box.

Former Nvidia (and Microsoft for that matter) devs are working on SteamOS but I haven't heard that Nvidia is doing so. AFAIK they're just working on their linux driver, and now openly communicating with the SteamOS devs. As far as contributing to SteamOS though, that's news to me if it's true.